Update packages and add vendor directory

vendor/github.com/josharian/intern/intern.go

@@ -0,0 +1,44 @@
+// Package intern interns strings.
+// Interning is best effort only.
+// Interned strings may be removed automatically
+// at any time without notification.
+// All functions may be called concurrently
+// with themselves and each other.
+package intern
+
+import "sync"
+
+var (
+	pool sync.Pool = sync.Pool{
+		New: func() interface{} {
+			return make(map[string]string)
+		},
+	}
+)
+
+// String returns s, interned.
+func String(s string) string {
+	m := pool.Get().(map[string]string)
+	c, ok := m[s]
+	if ok {
+		pool.Put(m)
+		return c
+	}
+	m[s] = s
+	pool.Put(m)
+	return s
+}
+
+// Bytes returns b converted to a string, interned.
+func Bytes(b []byte) string {
+	m := pool.Get().(map[string]string)
+	c, ok := m[string(b)]
+	if ok {
+		pool.Put(m)
+		return c
+	}
+	s := string(b)
+	m[s] = s
+	pool.Put(m)
+	return s
+}